An evolutionary approach to designing complex spreading codes for DS-CDMA

This paper proposes a novel evolutionary approach to spreading code design in direct sequence code division multiple access (DS-CDMA). Specifically, a multiobjective evolutionary algorithm (EA) is used to generate complex spreading sequences that are optimized with respect to the average mean-square cross- and/or autocorrelation (CC and/or AC) properties. A theoretical model is developed in order to demonstrate the optimality of the generated codes. The proposed algorithm enables spreading code design with no constraints on the code length. Furthermore, it is possible to generate K/spl ges/N codes of length N with very little cost in correlation properties. This results in significant capacity enhancement in DS-CDMA systems.     

An evolutionary approach for gene expression patterns

This study presents an evolutionary algorithm, called a heterogeneous selection genetic algorithm (HeSGA), for analyzing the patterns of gene expression on microarray data. Microarray technologies have provided the means to monitor the expression levels of a large number of genes simultaneously. Gene clustering and gene ordering are important in analyzing a large body of microarray expression data. The proposed method simultaneously solves gene clustering and gene-ordering problems by integrating global and local search mechanisms. Clustering and ordering information is used to identify functionally related genes and to infer genetic networks from immense microarray expression data. HeSGA was tested on eight test microarray datasets, ranging in size from 147 to 6221 genes. The experimental clustering and visual results indicate that HeSGA not only ordered genes smoothly but also grouped genes with similar gene expressions. Visualized results and a new scoring function that references predefined functional categories were employed to confirm the biological interpretations of results yielded using HeSGA and other methods. These results indicate that HeSGA has potential in analyzing gene expression patterns.     

An evolutionary approach to materialized views selection in a datawarehouse environment

A data warehouse (DW) contains multiple views accessed by queries. One of the most important decisions in designing a DW is selecting views to materialize for the purpose of efficiently supporting decision making. The search space for possible materialized views is exponentially large. Therefore heuristics have been used to search for a near optimal solution. In this paper, we explore the use of an evolutionary algorithm for materialized view selection based on multiple global processing plans for queries. We apply a hybrid evolutionary algorithm to solve three related problems. The first is to optimize queries. The second is to choose the best global processing plan from multiple global processing plans. The third is to select materialized views from a given global processing plan. Our experiment shows that the hybrid evolutionary algorithm delivers better performance than either the evolutionary algorithm or heuristics used alone in terms of the minimal query and maintenance cost and the evaluation cost to obtain the minimal cost     

An evolutionary spectrum approach to modeling non‐stationary fading channels

To evaluate mobile communication systems, it is important to develop accurate and concise fading channel models. However, fading encountered in mobile communication is usually non‐stationary, and the existing methods can only model quasi‐stationary or piecewise‐stationary fading instead of general non‐stationary fading. To address this, this paper proposes an evolutionary spectrum (ES)‐based approach to modeling non‐stationary fading channels. Our ES approach is more general than the existing piecewise‐stationary models and is capable of characterizing a general non‐stationary fading channel that has an arbitrary ES (or time‐varying power spectral density); our ES approach is parsimonious and is also able to generate stationary fading processes. As an example, we show how to apply our ES approach to generating stationary and non‐stationary correlated Nakagami‐m fading channel processes. Simulation results show that the ES of the channel gain process produced by our ES‐based channel model agrees well with the user‐specified ES, indicating the accuracy of our ES‐based channel model. Copyright © 2011 John Wiley & Sons, Ltd.     

一种电动汽车用GPS导航系统的设计

近年限于环境和能源的压力,电动汽车及相关产业受到国内外广泛关注.电动汽车正常工作的前提是需要充足的电能,以至于及时为车载动力电池补充电能成为关键.该文分别从硬件和软件两方面介绍了一种基于ARM+Windows CE 6.0平台的车载导航系统.该系统采用GPS和GPRS相结合的技术,实现了在电动汽车电池电量低的情况下,通...     

An output-feedback fuzzy approach to guaranteed cost control of vehicle lateral motion

This paper introduces a fuzzy guaranteed cost control approach for automated steering of a highway vehicle. The Takagi–Sugeno (T–S) fuzzy model is utilized to depict the dynamics of nonlinear time-varying lateral system. Based on the fuzzy model, an observer-based fuzzy controller is developed so that without knowing road’s curvature the vehicle can track center of the present lane on a curved highway section. Integrating H_∞ control and optimal control strategies, the fuzzy controller and observer are formulated by solving a minimization problem, which is to minimize a given quadratic performance function. Sufficient conditions to ensure minimum upper bound of the performance function are derived in terms of linear matrix inequalities (LMIs). Therefore, the designing work can be efficiently completed by applying the convex optimization techniques. Verified by computer simulation, the proposed method can perform well in driving safety and ride comfort.     

无人机视觉导航算法

为保证无人机着陆精度和安全性,提出了一种无人机自主着陆视觉导航位姿解算方法。首先对机载相机进行标定,获取相机参数;然后综合考虑地标形状和尺寸、地标角点几何分布和角点数量对位姿估计精度的影响,设计了T型着陆地标形状和尺寸参数,将地标轮廓提取和角点检测算法相结合,得到几何分布好、数量适中的8个角点用于位姿解算,保证了位姿解算精度;为减少LK （Lucas-Kanade）光流法稳定跟踪地标的处理时间,直接将提取的这8个角点作为LK光流法检测和跟踪的输入,保证了算法实时性;最后利用三维空间到二维像平面投影关系对飞行位姿参数进行实时解算。实验结果表明:算法具有较高估计精度,算法平均周期为76.756 ms （约13帧/s）,在速度较低的着陆阶段基本满足自主着陆视觉导航的实时性要求。     

An adaptive approach to spectral analysis of pattern-reversal visual evoked potentials

A method for spectral analysis of pattern-reversal visual evoked potentials (PRVEP's) is presented that results in spectral peaks of uniform width in the frequency domain for signals with a wide range of time-domain duration. Uniformity of spectral peak width is necessary for accurate comparison of spectra. The desired frequency domain characteristics can be achieved through the application of "tunable" data windows prior to transformation. The Io-sinh (Kaiser), Gaussian, and cosine-taper (Tukey) windows were evaluated as to their ability to produce power spectra with uniform spectral peak width. Objective comparison of power spectra is based on the "spectral parameter," which is a numerical index of power distribution. Application of the method to PRVEP waveforms of normal subjects (N = 20) and to a population of Alzheimer's Disease patients (N = 15) showed the Io-sinh window to be the most effective method, yielding correct classification of all normal and abnormal subjects. The Gaussian window also performed well, with only two misclassifications. Use of the rectangular window resulted in seven misclassifications. The tapered-cosine window was very limited in its applicability, and was about equal in performance to the rectangular window.     

航空飞行器天文自主导航定位技术

针对传统惯性/天文多星组合导航的不足和导航星选取不确定性,设计了一种基于捷联惯性/天文单星深度组合的长航时自主导航系统,通过对惯性导航和二维转台单星观测的误差特性进行建模,综合两者的优点,实现了单星观测角度和惯导解算数据的高精度融合;在高度通道方向,引入气压高度计对高度误差进行阻尼,通过卡尔曼滤波器对惯导误差进行最优估计,运用可观测性理论对系统进行分析,得到了最优导航星选取准则,有效地解决了在部分观测角度下算法性能下降的问题。仿真结果表明:该算法长时间导航定位精度优于传统算法,最优导航星选取准则有效地提高了算法的鲁棒性,具有较高的理论研究意义和工程应用价值。     

遥感卫星数据接收中的最优任务分配

在多地面站-多卫星的遥感数据接收条件下,通过定义卫星数据接收的任务集合将任务分配表达为任务集合和地面站集合之间的最优分配,并在构造代价函数的基础上实现最优分配算法在遥感数据接收任务管理中的应用。     

Depolarizing trihedral corner reflectors for radar navigation andremote sensing

A conventional trihedral corner reflector can be modified to present either a twist-polarizing or a circularly polarizing response by adding conducting fins of rectangular corrugations of prescribed dimensions and orientation to one of its interior surfaces. Since the modified reflector retains most of the mechanical ruggedness and ease of manufacture of the original, it is suitable for deployment in the field for extended periods as required in radar navigation and remote sensing applications. For most directions of incidence the response of the reflector is dominated by triple-bounce reflections from the interior and is a function of the size and shape of the reflecting panels, the dimensions of the corrugations, and the orientation of the reflector with respect to the radar. Experimental results show that prototype twist-polarizing and circularly polarizing reflectors respond as predicted     

陆用车载组合导航系统里程仪快速标定

为减小里程仪刻度因子误差对组合导航精度的影响,分析了安装误差以及轮胎内外温度与里程仪刻度因子的关系,提出组合导航系统中里程仪快速标定法,推导出组合导航系统卡尔曼滤波方程,进行系统仿真。结果表明,将里程仪刻度系数进行标定后,里程仪刻度系数误差明显提高两个量级,里程仪测量输出数据的准确度也明显提高,同时组合导航的定位精度也得到了提高。     

视觉导航用多功能路标设计与应用

优秀的路标设计,可以简化路标识别算法并提高机器人定位与导航的准确性和实时性。本文针对结构环境下的视觉导航系统,设计了一款多功能路标并给出了相应的应用算法。通过综合考虑拓扑结构、几何结构和色彩选取等的优化,设计的路标可以提供丰富的信息,而且具有较强的抗干扰能力。基于所设计的路标可以实现基于单帧图像中单个路标的机器人定位与导航,以及在大范围内基于序列路标的导航,并且可以准确估计序列路标中下一路标的位置。在具有较多干扰因素的大厅和走廊中进行的机器人定位与导航实验表明,即使采用未经校正的鱼眼镜头,机器人定位误差最大仍不超过5cm,示教再现导航误差最大不超过10cm;且在长距离导航实验中可实现方便、准确进行路标切换,有效提高导航的实时性和抗干扰性,证明了所设计路标的有效性。     

An evolutionary bargaining‐based approach for incentivized cooperation in opportunistic networks

Opportunistic networking enables users to communicate in an environment where connectivity is intermittent or unstable. However, such networking scheme assumes that mobile nodes voluntary cooperate, which cannot be guaranteed. Some nodes can simply exhibit selfish behavior and thus diminish the effectiveness of the approach. In this paper, a game scenario is formulated in which the nodes try to convince each other to participate in packets forwarding. Each node is considered as a player in this game. When a node comes in the communication range of another, a bargaining game starts between them as part of the message forwarding process. Both players try to have a mutual agreement on a price for message forwarding. We present a new incentive mechanism called evolutionary bargaining‐based incentive scheme (EBIS) to motivate selfish nodes to cooperate in data forwarding. In EBIS, a node negotiates with other nodes to obtain an agreeable amount of credit for its forwarding service. Nodes apply a sequential bargaining game and then adapt their strategies using an evolutionary model to maximize the probability of reaching an agreement. Unlike classical bargaining games, nodes in our model are boundedly rational. In addition, we use the evolutionary stable strategy (ESS) concept to determine the adaptive strategies for the nodes. The comparison of EBIS with a benchmarked model demonstrates that EBIS performs better in terms of packet delivery ratio and average latency.     

An optimization based approach to enhance the throughput and energy efficiency for cognitive unmanned aerial vehicle networks

Wireless Networks - Unmanned aerial vehicle (UAV) is a promising technology to serve as a mission-critical communication, where human operation or intervention is risky, dangerous, impossible or...     

A mechatronic sensing system for vehicle guidance and control

Magnetic sensing is used for control and guidance in intelligent transportation systems (ITS). This includes vehicle applications such as lane-keeping in intelligent cruise control as well as driver assistance in highway maintenance functions such as snow removal. This paper presents a new mechatronic magnetic sensing system for ITS. The new system has several advantages both in terms of its hardware design and its underlying reference detection algorithms, providing a significant improvement in performance, maintainability, and upgradability over existing systems. It is a mechatronic system in that it combines mechanical position sensing with electronics implementation of the hardware and the underlying algorithms.     

A lateral position sensing system for automated vehicle following

This paper investigates the use of photoresistive light sensor arrays as a possible lateral position sensing system for a vehicle, or several vehicles, following a lead vehicle under separate control. A brief motivation for the use of such a sensing array is followed by a derivation of an appropriate sensor layout. It is shown that the sensing array has several benefits, including cost, simplicity, redundancy, and near linearity. Experimental results are given for a scaled vehicle following manoeuvre using a simple lateral control strategy. The results show that the sensor array may be attractive for lateral alignment in vehicle-following manoeuvres     

无人机用MINS/光流组合导航系统

目的：减小因为惯导系统在无人机长航时飞行时的误差。方法：提出了一种用INS/光流/磁强计组合导航方案,基于扩展卡尔曼滤波,将INS与光流数据融合,估计无人机的速度和位置。当无人机静止或匀速运动时,将陀螺仪与加速计、磁强计的数据融合,估计无人机的姿态;当无人机加速或减速时,用陀螺仪估计无人机的姿态。结果：在不使用组合导航时,在大约50米的行驶路程中,就出现了近8米的累积误差,而使用组合算法后,所产生的误差不超过1米。结论：该方案有效的减少导航时的速度、位置和姿态的误差,提高导航精度。     

基于期望最大化算法的车载导航定位

随着GPS车载导航系统的普及,围绕车载导航系统性能的研究主要集中在了如何提高导航精度的问题上.然而,车载导航应用的特殊环境决定了传统的精度提高方法的局限性.文中首先简述了车载导航的特殊环境,然后在此基础上提出了利用EM(Expectation Maximization,期望最大化)算法提高导航状态解算精度的构想.通过使用平淡卡尔曼滤波,解决了期望最大化两步算法中的第一步即状态估计问题.基于实测数据的仿真结果证明,该方法能够有效地提高车载环境下接收机的定位精度和稳定性,进而提高车载导航的服务质量.